Delayed automatic volume control circuit



Sept. 5, 1939. E. KLOTZ 2,171,657

DELAYED AUTOMATIC VOLUME CONTPCL CIRCUIT Filed May 4, 1957 l l 'S/GIVAL 7 2 SOURCE I A'l'l'A'A'A A' B X .IIIIW W Er- E AVC CONTROLLEQ TUBES P INVENTOR ERNST KLOTZ ATTORNEY Patented Sept. 5, 1939 UNlTED STATES FATENT OFFICE Ernst Klotz, Berlin,

Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany Germany, a corporation of Application May 4, 1937, Serial No. 140,585

' In Germany May 30, 1936 2 Claims.

The present invention makes possible the use of diodes with a common cathode in a circuit with delayed automatic volume control. In accordance with the invention, the direct current 5 potential obtained by detection of the high frequency energy in the one diode of a duo-diode, is supplied aside from the tubes to be controlled, also to the positively biased anode of the other diode having the same cathode, and which last diode acts, until a definite high frequency amplitude is attained, as a short circuit for the control potential.

An example embodying the idea of the invention is shown in the figure. The high frequency signal energy is supplied to the oscillatory circuit S, and detected in the diode I. The

audio frequency potential NF appearing across the load resistor B is, furthermore, supplied to the following tube, while the direct current voltage component is supplied through the resistor W1 to the point P and from there to the controlled high frequency stages. The control potential is likewise supplied from point P to the anode of the .diode 2, which is positively biased 25 with 3 volts, for instance, by the voltage divider W3, W4 across the resistor W2.

As long as the positive biasing potential at the diode 2 is not eliminated by the negative control potential appearing at resistor B, the diode acts as a conductor and thus as a short circuit in that it connects the point P to ground. The control potential produced at the resistor B cannot act at point P and at the tubes to be controlled. The resistors W1 and W4 must be sufficiently high since the series connection thereof is in parallel to the load resistor. Obviously,

it is within the scope of the invention to carry out the detection, which serves for obtaining the audio frequency voltage, with a third detector, so that the duo-diode l, 2 only serves for producing the control potential. In this case, at small input amplitudes, no disadvantage exsists if the load resistor of the diode producing the control potential is directly short-circuited by the other diode. By way of example, the following constants may be used: B=0.3MQ; W1:0.5MQ; WZIIMQ.

What is claimed is:

1. In a wave reception system, a tube having a single cathode and at least two anodes, a path between one anode and the cathode including a wave input circuit and load impedance in series, means establishing the second anode at a positive potential relative to the cathode, a gain control circuit connected to a point of the impedance which is at a negative direct current voltage with respect to said cathode, and means connecting said impedance point to the said second anode to render the diode provided by the second anode and the cathode non-conductive when said point assumes a predetermined negative voltage value.

2. In combination with a signal rectifier including a load impedance to develop a direct current voltage for automatic volume control action, a diode, means for maintaining the latter in a conductive state, and means for connecting the impedance to the diode to render said voltage ineffective until it attains a value sufiicient to render the diode non-conductive, said rectifier and diode being provided by a tube having a single cathode and two anodes.

ERNST KLOTZ. 

